Joshua struggled to victory over Carlos Takam in Cardiff on Saturday (28 October).

Boxing promoter Frank Warren believes comparisons between Anthony Joshua and Muhammad Ali are "beyond stupid" and admits he has not been too impressed by the unified world heavyweight champion's title fights.

Joshua retained his titles with a controversial 10th-round stoppage against Carlos Takam at the Principality Stadium on Saturday (28 October) but left much to be desired as he struggled to victory over the journeyman Cameroonian, who was a late substitute for original challenger Kubrat Pulev.

The bout against Takam's added further gloss to Joshua's professional career record, which now stands at 20 victories and zero defeats. However, Warren does not think the fights that led to him becoming world heavyweight champion are a patch on Ali's classic encounters.

Ali endured brutal wars against the likes of George Foreman and Joe Frazier and became world champion aged just 22 when he swept aside Sonny Liston in 1964. Joshua's only title fights have come against Klitschko, Takam and Charles Martin, who lasted just two rounds in the ring with the former Olympic gold medallist.

Bigger tests are sure to come for Joshua – Deontay Wilder, Joseph Parker and perhaps even Tyson Fury are waiting in the wings – but Warren, who has been involved in boxing for the best part of 40 years, does not think the Englishman is near the level of Ali, who sadly passed away last year.

"Let's get it right. Tyson Fury had to vacate the IBF title. AJ picked up the title by fighting Charles Martin, who is possibly the worst heavyweight champion I've ever seen in boxing," Warren said on talkSPORT.

"He did what he had to do against Martin, he won the title. He fought Wladimir Klitschko and fought Dillian Whyte. Klitschko was coming out of 18 months of inactivity after being soundly beaten by Tyson Fury and Dillian Whyte is a decent young professional but he is not what you consider a world-ranked opponent. Dillian Whyte wobbled him.

"Klitschko had him on the floor. It was one of the most exciting heavyweight fights I have seen for years, it was a great fight, but it wasn't Muhammad Ali, it wasn't Joe Frazier, it wasn't George Foreman, it wasn't Kenny Norton, it wasn't Earnie Shavers, all these guys.

"Joshua has had three title fights and comparing him with Ali? It is beyond stupid."

Despite disparaging comparisons between the two, Warren did admit that Joshua's heart and stamina is akin to that of Ali. The esteemed promoter has been impressed by the Watford-born fighter's ability to regroup during fights but expressed concerns over his ability to take punishment, something Ali was universally known for.

"He has got a heart like Ali. Ali had a big heart and AJ has got a tremendous heart. He has not got a bad engine, I've seen him a couple of times where he has got a second wind in fights.

"But what he has not got is Ali's chin. Anthony Joshua does not have Ali's chin, that is for sure."